Expansion of a Thermometer

1. The problem statement, all variables and given/known data
(a) The tube of a mercury thermometer (made of Pyrex glass) has an inside diameter of 0.140 mm. The bulb has a volume of 0.275 cm3. How far will the thread of mercury move when the temperature changes from 10.5 degrees Celsius to 33.0 degrees Celsius?

(b) Determine a formula for the change in length of the mercury column in terms of relevant variables. Ignore tube volume compared to bulb volume.

3. The attempt at a solution
I calculated the change in the volume of the bulb via equation I, but I am unsure where to head from here. Without knowing the height of the mercury within the thermometer (save for the temperature intervals), I am unsure of how to find the change in volume of the tube or the change in volume of the mercury itself. Any hints?